On Android, “Video Downloader for Instagram” by InShot Inc. or “Reels Downloader” let you copy-link → paste → save the reel locally, while on iOS “Reposter for Instagram” (no login needed) does the same; stick to store-listed apps that work via the share-link method so you never have to enter your Instagram credentials. Always clear the app’s cache/permissions afterward to keep your account and device safe.